Method and circuit for demultiplexing an optical signal

Abstract

A system and method are disclosed for demulitplexing closely spaced channels carrying optically encoded data. A composite optical signal having data channels corresponding to center wavelengths lambda 1, lambda 2, lambda 3, lambda 4, . . . lambda n are separated into two composite optical signals of first of which comprises data channels corresponding to center wavelengths lambda 1, lambda 3, . . . lambda n and a second which comprises data channels corresponding to center wavelengths lambda 2, lambda 4, . . . lambda n-1, wherein adjacent channels center wavelengths are separated from one another by a distance "d". A periodic multi-cavity Fabry-Per+E,cir o+EE t etalon having a free spectral range of "2d" is coupled to a circulator for launching an input beam. The first of the two composite optical signals carrying channels 1, 3, . . . n is reflected from the input port of the etalon and the second of the of the two optical signals carrying channels 2, 4, . . . n-1 is transmitted through the etalon. After the two signals are separated, further separation can be achieved by using conventional dichroic filters.

What is claimed is: 
     
       1. In a system wherein a plurality of contiguous data channels comprising a plurality of non-contiguous channels 1, . . . n centered at wavelengths of light λ1 . . . λn, respectively, multiplexed within a single optical signal, wherein the signal comprises at least a data channel spaced having a center wavelength spaced from a center wavelength of a subsequent or next data channel by a distance of "d" nanometers, and wherein λ . . . <λn, and wherein n is an integer, a method of demultiplexing or de-interleaving data channels corresponding to at least some non-contiguous data channels from the single optical signal, comprising the steps of: launching the single optical signal into an input port of an etalon, the etalon having a free spectral range (or period) corresponding to substantially "k2d", where "k" is an integer >0;   extracting only a portion of the launched optical signal in the form of a reflected signal captured from an output port on the etalon comprising only data channels spaced by a distance "k2d".   
     
     
       2. A method of demultiplexing channels of light as defined in claim 1, wherein k=1. 
     
     
       3. A method of demultiplexing channels of light as defined in claim 1, wherein the etalon is a multi-cavity etalon. 
     
     
       4. A method of demultiplexing channels of light as defined in claim 1 wherein the etalon has an output port at each of its end faces, and wherein an output response is captured at each port, the output responses captured at each port being shifted by d nanometers. 
     
     
       5. A method of demultiplexing channels of light as defined in claim 3, wherein the multi-cavity etalon has at least 3 cavities, and wherein the distance between cavity mirrors is substantially the same. 
     
     
       6. A method as defined in claim 1, wherein the input port and the output port are the same port. 
     
     
       7. In a system wherein a plurality of contiguous data channels 1, 2, 3, . . . n centered at wavelengths of light λ1, λ2, λ3, . . . λn, respectively, multiplexed within a single optical signal, wherein a center wavelength corresponding to at least a data channel within the signal is spaced from a center wavelength of a subsequent or next channel by a distance of "d" nanometers, and wherein λ1<λ2<λ3, . . . <λn, and wherein n is an integer, a method of de-interleaving data channels of light corresponding to at least channels 1 and 3 from the single optical signal, comprising the steps of: launching the single optical signal into an input port of an etalon, the etalon having a free spectral range (or period) corresponding to "2d";   extracting a portion of the launched optical signal in the form of a reflected signal captured from a port of the etalon comprising at least channels 1 and 3, spaced by a distance "2d" without capturing light corresponding to channel 2 from the same port of the etalon.   
     
     
       8. A method as defined in claim 7, further comprising the step of extracting a portion of the launched optical signal in the form of a transmitted signal captured from a another port at another side of the etalon comprising at least two second extracted channels including channel 2, said channels spaced by a distance "2d", wherein the at least two second channels are separated by a distance "d" from the two first extracted channels. 
     
     
       9. A method as defined in claim 8 wherein the distance "d" is substantially equal to 0.8 nanometers. 
     
     
       10. The method as defined in claim 9, wherein the etalon, the etalon having a free spectral range (or period) corresponding to "2d", is a multi-cavity etalon. 
     
     
       11. An etalon for use in demultiplexing or multiplexing data channels in an optical system, the data channels being contiguous data channels 1, 2, 3, . . . n centered at wavelengths of light λ1, λ2, λ3, . . . λn, respectively, multiplexed within a single optical signal, wherein at least some data channels within the signal have a center wavelength spaced from a center wavelength of a subsequent or next data channel by a distance of "d" nanometers, and wherein λ1<λ2<λ3, . . . <λn, and wherein n is an integer, the etalon being a multi-cavity etalon having a free spectral range (or period) corresponding to "2d", the etalon having an input port for launching the signal comprising the plurality of data channels, and the etalon having coupling means optically coupled with the input port, said coupling means for providing the signal to the etalon, and having port for receiving a portion of the signal reflected from the multi-cavity first etalon. 
     
     
       12. A system as defined in claim 11, wherein in the coupling means is an optical circulator. 
     
     
       13. A system as defined in claim 11 further comprising a second multi-cavity etalon, having a free spectral range (or period) corresponding to "2d", and having a response that is substantially the same as that of the multi-cavity first etalon however shifted by `d` nanometers. 
     
     
       14. A system as defined in claim 13, wherein the first etalon and the second etalon are optically coupled. 
     
     
       15. A system as defined in claim 14, wherein the first etalon is provided to substantially transmit or reflect a first group of wavelengths, and wherein the second etalon is provided to transmit or reflect a second group of wavelengths. 
     
     
       16. A system as defined in claim 11, further comprising additional different filter means for further demultiplexing the at least two signals. 
     
     
       17. In a system wherein a plurality of contiguous data channels 1, 2, 3, . . . n centered at wavelengths of light λ1, λ2, λ3, . . . λn, respectively, are multiplexed within a single optical signal, wherein at least a data channel within the signal has a center wavelength is spaced from a center wavelength of a subsequent or next data channel by a distance of "d" nanometers, and wherein λ1<λ2<λ3, . . . <λn, and wherein n is an integer, a method of de-interleaving data channels corresponding to at least data channels 1 and 3 from the single optical signal, comprising the steps of: launching the single optical signal into an input port of an etalon, the etalon having a free spectral range (or period) corresponding to "2d";   extracting only a portion of the launched optical signal in the form of a reflected signal captured from an input port side of the etalon comprising at least two first extracted data channels, spaced by a distance "2d".   
     
     
       18. In a system having a plurality of contiguous data channels 1, 2, 3, . . . n centered at wavelengths of light λ1, λ2, λ3, . . . λn, respectively, the data channels being on two separate waveguides such that data channels corresponding to wavelengths λ1, λ3, are on a first optical waveguide, and data channels corresponding to wavelengths λ2, λ4 are on a second optical waveguide, wherein at least a data channel has a center wavelength is spaced from a center wavelength of a subsequent or next sequential data channel by a distance of "d" nanometers, and wherein λ1<λ2<λ3, . . . <λn, and wherein n is an integer, a method of interleaving data channels corresponding to at least data channels 1, 2, 3 and 4 into a single optical signal, comprising the steps of: launching at least light having wavelengths λ1, λ3 corresponding to data channels 1 and 3 into a first port on one side of an etalon by optically coupling the first waveguide with the first port, the etalon having a free spectral range (or period) corresponding to "2d"; launching at least light having wavelengths λ2, λ4 corresponding to at least data channels 2 and 4 into a second port on an opposite side of an etalon from the first port by optically coupling the second waveguide with the second port; and,   extracting a composite optical signal from a port on one of the sides of the etalon, the composite optical signal comprising wavelengths of light corresponding to data channels 1, 2, 3, and 4.